This invention relates to high-expansion manganese alloys and, more particularly, to a high-expansion manganese-copper-nickel alloy having improved strength and electrical resistivity and shaped articles made therefrom.
High-expansion manganese alloys containing copper and nickel have long been provided for a wide variety of uses, as for example, bimetal strip in thermally responsive control device. For example, Dean and Anderson U.S. Pat. No. 2,234,748, Mar. 11, 1941, discloses an alloy containing 50 to 85% manganese, 2 to 48% copper, and 2 to 35% nickel with the sum of the Mn, Cu and Ni being substantially 100%. Specific compositions contain 75% Mn with 5% Ni and 20% Cu, with 10% Ni and 15% Cu, with 15% Ni and 10% Cu, and with 20% Ni and 5% Cu. The compositions, when treated as described are asserted to have a temperature coefficient of expansion of from about 24.5 to as high as 27.0.times.10.sup.-6 /.degree. C. Dean U.S. Pat. No. 2,317,979, May 4, 1943, relates to Mn--Ni--Zn--Cu alloys and sets forth a composition containing 72% Mn, 18% Cu and 10% Ni.
Dean U.S. Pat. No. 2,329,698, Sept. 21, 1943 relates to the preparation of manganese alloys by means of powder metallurgy techniques in which powdered electrolytic manganese is mixed with powdered copper and heated in the absence of oxygen and nitrogen to achieve diffusion of the copper into the manganese. When copper cannot be tolerated, other procedures for obtaining ductile manganese powder include using nickel in place of copper or heating the manganese in ammonia gas at about 450.degree. C. and then, in the absence of oxygen or in an atmosphere of nitrogen, to a temperature of about 1000.degree. C.
Averbach, Metals and Alloys, July 1941 pp. 47-51, at page 49 lists a large number of Mn, Cu, Ni alloys including 80% Mn, 10% Cu, 10% Ni and points out some of the effects of composition variations of those three elements.
Gottlieb et al U.S. Pat. No. 3,765,846, Oct. 16, 1973 relates to thermostatic bimetals in which the high-expansion material contains 15.5-22.5% nickel, an amount of copper such that the sum of the percent copper and one-half the percent nickel is 13.75-16.75% and the balance manganese. In effect, the copper content can vary from 2.5-9.0% and the manganese content from about 68.5-82% (with incidental impurities). The preferred compositions are identified as those containing 15.5-18.5% nickel which results in a corresponding copper content of 4.50-9.00%. British Patent No. 526,093 (Consolidated Mining and Smelting Company of Canada, Ltd.) 1940, relates to alloys of Mn and Cu containing at least 40% Mn and one or more of the elements Ni, B, Al, Sn, Ag, Si and Be all added to the pure manganese for the purpose of providing ductile alloys, pure manganese alone being brittle. A composition containing 80% Mn also contains 10% Cu, 10% Ni and 0.02% B.
Thus, it has long been recognized in connection with the ternary system Mn--Cu--Ni that variations in the proportions of the elements have a significant effect on the alloys' thermal expansivity and electrical resistivity. However, such manganese alloys containing copper and nickel with or without relatively small amounts of additional elements have hitherto been difficult to control so as to ensure in a shaped article the desired high-thermal expansion and other desired properties.